Wall surface water circulation system capable of reducing scattering of irradiation chamber

Abstract

The invention belongs to the technical field of ionizing radiation metrological verification, and particularly discloses a wall surface water circulation system capable of reducing scattering of an irradiation chamber, which comprises a box body with a flat structure, a boric acid solution is arranged in the box body, so that a water wall is formed in the box body, the thickness of the water wall is 2-5cm, and the concentration of the boric acid solution is 2.7-4.6%; the top of the box body is provided with a water injection port and an exhaust port, the water injection port is used for injecting a boric acid solution into the box body, the lower part of the box body is provided with an emptying port, and the box body is made of plastic, iron or aluminum. The anti-scattering coating has a good anti-scattering function and anti-scattering stability, and meanwhile, the economic cost can be effectively reduced, and the fire load in an irradiation room can be relieved.

Description

Technical Field

[0001] The invention belongs to the technical field of ionizing radiation measurement and verification, and particularly relates to a wall water circulation system capable of reducing scattering in an irradiation room. Background Art

[0002] With the comprehensive upgrade of the public's understanding of ionizing radiation, the demand for ionizing radiation measurement and verification is no longer limited to a few fields such as scientific research, education, and radiation health. More and more scientific and technological innovation companies are investing in this field.

[0003] There are generally three types of reference radiation sources used in neutron radiation metrology verification:

[0004] (1) Neutrons produced by isotope neutron sources (including sources in moderators);

[0005] (2) Neutrons produced by charged particle nuclear reactions in accelerators;

[0006] (3) Neutrons produced by nuclear reactors.

[0007] At present, the most commonly used neutron reference radiation is the first type, that is, installing a storage container or digging a storage well in a standard irradiation room. When in use, the neutron source transmission / lifting device is used to raise the source to complete the irradiation operation; after the operation is completed, the neutron source is lowered by the neutron source transmission / lifting device and falls back to the safe storage position.

[0008] In the above metrological verification process, the neutrons emitted from the neutron source will be scattered back to the calibration position by the shielding wall of the irradiation room in a complex way, and will have a certain impact on the verification work. This impact can be determined by neutron transport calculation or by experimental measurement under specific conditions; according to the requirements of "Neutron Reference Radiation Part 2: Calibration Basis of Radiation Protection Instruments Related to Basic Quantities Characterizing Radiation Fields" GB / T 14055.2-2012: In any case, the contribution of scattered neutrons should not increase the instrument reading at the calibration point by more than 40%.

[0009] Since the influence of room scattered neutrons is related to the size, shape and structure of the irradiation room and the distance between the instrument to be tested and the neutron source; the smaller the room size and the farther away from the neutron source (i.e. the closer to the shielding wall of the irradiation room), the greater the room scattering influence. Therefore, in the past standard neutron irradiation room design activities, as long as conditions permit, the irradiation room can be designed according to the shape and size given in Appendix B of GB / T 14055.2-2012; but for some projects with tight land use plans, the irradiation room cannot be designed according to the standard appendix, and additional scatter reduction treatment is required.

[0010] The commonly used and efficient scatter reduction measure is to lay boron-containing polyethylene boards on the walls and floors around the irradiation room. Boron-containing polyethylene boards can be used to make ceilings. The principle is the interaction between boron-containing polyethylene and neutrons, which can be divided into two steps:

[0011] (1) The carbon and hydrogen atoms (mainly hydrogen atoms) in polyethylene slow down neutrons;

[0012] (2) Boron atoms capture thermal neutrons, thereby reducing the thermal neutron flux of chamber scattered neutrons:

[0013] 10 B+n= 7 Li+α+γ

[0014] 10 B(n,α) 7 The α particles produced by the Li reaction are absorbed by the material, neutralized into helium and volatilized (α particles are helium nuclei). However, the use of boron-containing polyethylene plates as standard neutron irradiation room scatter reduction materials is expensive, and boron carbide (B4C) and polyethylene (PE) materials are not chemically bonded; under the action of the neutron irradiation field, the material will accelerate aging, causing the boron carbide particles to fall off from the polyethylene, weakening the scatter reduction effect. Summary of the invention

[0015] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a wall water circulation system that can reduce the scattering in the irradiation room. The present invention has good scattering reduction function and scattering reduction stability, and can also effectively reduce economic costs and reduce the fire load in the irradiation room.

[0016] The technical solution of the present invention is achieved in this way:

[0017] A wall water circulation system capable of reducing scattering in an irradiation room comprises a box body with a flat structure, wherein a boric acid solution is arranged in the box body, thereby forming a water wall in the box body, wherein the thickness of the water wall is 2 to 5 cm, and the concentration of the boric acid solution is 2.7 to 4.6%. A water injection port and an exhaust port are arranged on the top of the box body, wherein the water injection port is used to inject the boric acid solution into the box body, and an exhaust port is arranged at the bottom of the box body, and the box body is made of plastic, iron or aluminum.

[0018] Furthermore, a vertical guide plate is provided in the box body, and the vertical guide plate is arranged along the width direction of the box body and close to one of the side plates corresponding to the width of the box body. The edges on both sides of the vertical guide plate are seamlessly connected to the inner wall of the box body, and the upper and lower ends of the vertical guide plate are at a certain height from the top and bottom of the box body, thereby forming a flow hole. A number of horizontal guide plates are provided between the vertical guide plate and the other side plate corresponding to the width of the box body. The horizontal guide plates are staggered and spaced apart, thereby forming a serpentine channel. The top and bottom horizontal guide plates are connected to the vertical guide plates.

[0019] Auxiliary heating equipment is provided at the bottom of the box away from the vertical guide plate to heat the boric acid solution so that the boric acid solution forms thermal convection in the box to ensure that the temperature is higher than the saturation temperature of the boric acid solution and avoid boric acid crystallization.

[0020] Furthermore, an impeller is provided between two adjacent transverse guide plates to facilitate rotation under convection to stir the boric acid solution.

[0021] Furthermore, the impeller is externally connected to a driving mechanism to facilitate driving the impeller to rotate.

[0022] Furthermore, a monitoring mechanism is provided in the box, and the monitoring mechanism is used to monitor the pH value and concentration of the boric acid solution in real time, so as to facilitate the injection of lithium hydroxide solution to adjust the pH to neutral.

[0023] Furthermore, the drain port can be connected to a fire protection system through a pipeline, and a switch valve is provided on the pipeline to facilitate controlling the switch valve to open and pump out the boric acid solution to extinguish the fire when a fire occurs.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention uses a more economical boric acid solution instead of a boron-containing polyethylene sheet to achieve a reduced room scattering effect, which can effectively reduce economic costs and reduce the fire load in the irradiation room. When necessary, the boric acid solution can be used as a fire water source. The auxiliary heating equipment can also be used as a heat source for controlling the temperature and humidity of the irradiation room environment, reducing dependence on an independent temperature and humidity control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 -Schematic diagram of the structure of the present invention.

[0027] Figure 2-2 Comparison of the scattering reduction effects of the cm boric acid solution box and the 5cm boric acid solution box.

[0028] Figure 3-2 Comparison of the scattering reduction effects of cmBPE and 5cm boric acid solution boxes.

[0029] Among them: 1-box; 2-water inlet; 3-exhaust port; 4-drain port; 5-vertical guide plate; 6-lateral guide plate; 7-auxiliary heating equipment; 8-impeller. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0031] See also Figure 1A wall water circulation system capable of reducing scattering in an irradiation room comprises a flat box 1, wherein a boric acid solution is arranged in the box 1, thereby forming a water wall in the box, wherein the thickness of the water wall is 2 to 5 cm, and the concentration of the boric acid solution is 2.7 to 4.6%. A water injection port 2 and an exhaust port 3 are arranged on the top of the box 1, wherein the water injection port 2 is used to inject the boric acid solution into the box 1, and an emptying port 4 is arranged at the bottom of the box 1, wherein when the quality of the boric acid solution does not meet the requirements, the emptying port is used to discharge the boric acid solution in the box, and the box 1 is made of, but not limited to, plastic or metal materials such as iron and aluminum.

[0032] The box contains a boric acid solution, which is not limited to natural boric acid, including boric acid 10 The isotope separation product with higher B enrichment can be slowed down by hydrogen atoms in the boric acid solution, and then the thermal neutrons are captured by boron-10 atoms to reduce the thermal neutron component in the scattered neutrons in the standard neutron irradiation room, so as to achieve the scattering reduction function.

[0033] The box here has a certain pressure-bearing capacity. If it is made of metal material, in order to reduce neutron scattering, light metal material with low atomic number and low density can be selected. If engineering plastics are used, radiation-resistant plastics should be selected, that is, it can be guaranteed not to degrade and not to lose strength under neutron irradiation field.

[0034] During specific implementation, a vertical guide plate 5 is vertically provided in the box body, and the vertical guide plate 5 is arranged along the width direction of the box body 1 and close to one of the side plates corresponding to the width of the box body. The left and right edges of the vertical guide plate are seamlessly connected to the inner wall of the box body, and the upper and lower ends of the vertical guide plate are at a certain height from the top and bottom of the box body, thereby forming a flow hole, and a plurality of transverse guide plates 6 are horizontally provided between the vertical plate 5 and the other side plate corresponding to the width of the box body 1. All transverse guide plates 6 are staggered up and down at intervals, and the three side edges of one transverse guide plate of two adjacent transverse guide plates 6 are correspondingly connected to the vertical guide plate and the corresponding two inner walls of the box body, and the other side edge is at a certain distance from the corresponding side plate of the box body, and the three side edges of the other transverse guide plate are correspondingly connected to the corresponding three inner walls of the box body, and the other side is convenient for being at a certain distance from the vertical guide plate, and at the same time, one side edge of the transverse guide plate 6 located at the top and the bottom are both connected to the vertical guide plate 5.

[0035] An auxiliary heating device 7 is provided at the bottom of the box away from the vertical guide plate to heat the boric acid solution so that the boric acid solution forms heat convection in the box 7 to ensure that the temperature is higher than the saturation temperature of the boric acid solution to avoid boric acid crystallization.

[0036] In this way, it is equivalent to installing a transverse guide plate on the wide side separated by the vertical guide plate. The transverse guide plates are arranged in a staggered manner. When the auxiliary heating equipment is working, the boric acid solution can form thermal convection in the box. The boric acid solution can rise in a serpentine shape under the guidance of the transverse guide plate, and then flow into the vertical channel between the vertical guide plate and the side plate of the box from the flow hole between the vertical guide plate and the top of the box, and then flow back to the bottom of the box, so that the boric acid solution circulates in the box, ensuring that the boric acid in the boric acid solution will not crystallize and precipitate, thereby ensuring the scattering reduction effect.

[0037] In specific applications, the auxiliary heating equipment is turned on as needed. When the irradiation chamber is not performing operations, the auxiliary heating equipment is turned off and is in cold standby status. When there are operating tasks, the boric acid concentrations at two remote points can be sampled and tested in advance. If the difference is large, the auxiliary heating equipment can be turned on in advance. When the boric acid concentrations at the two remote points are similar and tend to the theoretical value, the neutron metrology verification operation can be carried out normally.

[0038] At the same time, the auxiliary heating equipment can be used as a heat source for temperature and humidity control in the irradiation room to ensure that the neutron measurement verification process is in a stable environmental state, which is convenient for correction work after verification. According to GB / T 14055.2-2012, the temperature and humidity conditions of the irradiation room should be as close as possible to 21°C, relative humidity 50%, and air pressure 100.4kPa.

[0039] In specific implementation, an impeller 8 is provided between two adjacent transverse guide plates 6 to facilitate rotation under convection to stir the boric acid solution, thereby making the boric acid concentration distribution more uniform.

[0040] In a specific implementation, the impeller 8 is externally connected to a driving mechanism to drive the impeller 8 to rotate. When the driving force provided by thermal convection is insufficient and the boric acid solution in the water tank needs to be quickly and evenly distributed, the driving mechanism is turned on to drive the impeller to rotate and stir the boric acid solution, so that the boric acid solution circulates in the tank and the concentration of the boric acid solution is quickly and evenly distributed.

[0041] During specific implementation, a monitoring mechanism is provided in the box 1, which is used to monitor the pH value and concentration of the boric acid solution in real time, so as to facilitate the injection of lithium hydroxide solution to adjust the pH to neutrality and eliminate the corrosiveness of the boric acid solution to the box material. At the same time, it can also effectively monitor the quality of the boric acid solution to prevent the deterioration of the boric acid solution and affect the scattering reduction effect.

[0042] In a specific implementation, the drain port is connected to a fire protection system through a pipeline, and a switch valve is provided on the pipeline to facilitate controlling the switch valve to open and pump out boric acid solution to extinguish the fire when a fire occurs.

[0043] In this way, when extreme conditions occur in the irradiation room, such as a fire, the boric acid solution in the box can be used as a temporary source of fire water, and the boric acid solution can be pumped out in time to participate in fire extinguishing.

[0044] The solubility of boric acid is shown in Table 1:

[0045] Table 1 Boric acid solubility table

[0046] Temperature: ℃ Solubility: g Temperature: ℃ Solubility: g 0 2.77 40 8.90 10 3.65 50 11.39 20 4.87 60 14.89 25 5.74 80 23.54 30 6.77 100 38.00

[0047] 1. Inject boric acid solution prepared with natural boric acid into two boxes of different thicknesses. The thickness of the boric acid solution water wall in one box is 2 cm, and the thickness of the boric acid solution water wall in the other box is 5 cm. The water temperature of the box is set to 20°C, and the concentration of the boric acid solution is 4.64%. The comparison of the scattering reduction effect is shown in the figure below. Figure 2 shown.

[0048] 2. Inject natural boric acid solution into the box, set the water temperature of the box to 20℃, and the concentration of the boric acid solution to 4.64%, to obtain a boric acid solution box with a boric acid solution water wall thickness of 5cm. The comparison of the scattering reduction effect of the 5cm boric acid solution box and the 2cm boron-containing polyethylene composite board is shown in the figure below. Figure 3 As shown. The boric acid solution and the boron-containing polyethylene composite plate anti-scattering material 10 The B content table is shown in Table 2.

[0049] Table 2 Scattering reduction materials 10 B Content Table

[0050]

[0051] Depend on Figure 3 It can be seen that the effect of boric acid solution in absorbing low-energy neutrons is worse than that of boron-containing polyethylene composite board, but it has certain advantages at the high-energy end. In the irradiation chamber of the embodiment (11.8×9.7×8.6m), the 241Am-Be neutron source is placed at the geometric center of the irradiation chamber. Under the action of a certain response function, the scattering effect of the 5cm boric acid solution box is better than that of the 2cm boron-containing polyethylene composite board. At 6m away from the neutron source, using a 5cm boric acid solution box, scattering increases the instrument reading by 38.41% <40%; using a 2cm boron-containing polyethylene composite board, scattering increases the instrument reading by 55.14%.

[0052] Two types of material cost estimates:

[0053] Irradiation chamber surface area A:

[0054] A=(11.8×9.7+11.8×8.6+9.7×8.6)×2=598.72m 2

[0055] (1) Volume of boron-containing polyethylene composite board:

[0056] V1=598.72×0.02=11.97m 3

[0057] Boron-containing polyethylene composite board quality:

[0058] m1=ρ1V1=0.97×11.97=11.62t

[0059] Calculated at ￥30.00 / kg, the construction cost of using 2cmBPE is: 11.62×1000×30=348,455 yuan;

[0060] (2) Volume of boric acid solution:

[0061] V2=598.72×0.05=29.94m 3

[0062] Boric acid solution quality:

[0063] m2=ρ2V2=1.0×29.94=29.94t

[0064] Boric acid mass:

[0065] m3=m2c=29.94×4.64%=1.39t

[0066] Boric acid is priced at ￥5.80 / kg, and deionized water is priced at ￥0.72 / kg, then:

[0067] Boric acid: 1.39 × 1000 × 5.8 = 8,062 yuan

[0068] Deionized water: (29.94-1.39)×1000×0.72=20,556 yuan

[0069] Total cost: 28,618 yuan

[0070] The cost of using boric acid solution is only 8.2% of that of using boron-containing polyethylene composite board. It can be seen that the use of boric acid solution can effectively reduce economic costs.

[0071] Finally, it should be noted that the above embodiments of the present invention are only examples for illustrating the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes and modifications can be made based on the above description. It is impossible to list all implementation methods here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A wall water circulation system capable of reducing scattering in an irradiation room, characterized in that: The invention comprises a box body with a flat structure, wherein a boric acid solution is arranged in the box body, thereby forming a water wall in the box body, wherein the thickness of the water wall is 2-5 cm, and the concentration of the boric acid solution is 2.7-4.6%. A water inlet and an exhaust port are arranged on the top of the box body, wherein the water inlet is used to inject the boric acid solution into the box body, and an exhaust port is arranged at the bottom of the box body, and the box body is made of plastic, iron or aluminum.

2. A wall water circulation system capable of reducing scattering in an irradiation room according to claim 1, characterized in that: A vertical guide plate is provided in the box body, and the vertical guide plate is arranged along the width direction of the box body and close to one of the side plates corresponding to the width of the box body. The edges of the two sides of the vertical guide plate are seamlessly connected to the inner wall of the box body. The upper and lower ends of the vertical guide plate are at a certain height from the top and bottom of the box body, thereby forming a flow hole. A plurality of transverse guide plates are provided between the vertical guide plate and the other side plate corresponding to the width of the box body. The transverse guide plates are staggered and spaced apart, thereby forming a serpentine channel. The transverse guide plates at the top and bottom are connected to the vertical guide plates; Auxiliary heating equipment is provided at the bottom of the box away from the vertical guide plate to heat the boric acid solution so that the boric acid solution forms thermal convection in the box to ensure that the temperature is higher than the saturation temperature of the boric acid solution and avoid boric acid crystallization.

3. A wall water circulation system capable of reducing scattering in an irradiation room according to claim 2, characterized in that: An impeller is arranged between two adjacent transverse guide plates so as to rotate under the action of convection to stir the boric acid solution.

4. A wall water circulation system capable of reducing scattering in an irradiation room according to claim 3, characterized in that: The impeller is externally connected to a driving mechanism to facilitate driving the impeller to rotate.

5. The wall water circulation system capable of reducing scattering in an irradiation room according to claim 1, characterized in that: A monitoring mechanism is provided in the box, and the monitoring mechanism is used to monitor the pH value and concentration of the boric acid solution in real time, so as to facilitate the injection of lithium hydroxide solution to adjust the pH to neutral.

6. A wall water circulation system capable of reducing scattering in an irradiation room according to claim 1, characterized in that: The drain port can be connected to the fire protection system through a pipeline, and a switch valve is provided on the pipeline to facilitate controlling the switch valve to open and pump out the boric acid solution to extinguish the fire when a fire occurs.

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